Cooper-Frye sampling with short-range repulsion

TL;DR

This paper introduces the FIST sampler, a new method for incorporating short-range repulsion in particle sampling, improving accuracy and flexibility in modeling heavy ion collision observables.

Contribution

The FIST sampler integrates short-range repulsion via rejection sampling into the Cooper-Frye procedure, enabling more precise and extendable simulations of particle distributions in heavy ion collisions.

Findings

Quantifies the impact of excluded volume on proton number cumulants.

Demonstrates improved accuracy over analytical approximations.

Shows flexibility of the method for various observables.

Abstract

This work incorporates the effect of short-range repulsion between particles into the Cooper-Frye hadron sampling procedure. This is achieved by means of a rejection sampling step, which prohibits any pair of particles from overlapping in the coordinate space, effectively modeling the effect of hard-core repulsion. The new procedure -- called the FIST sampler -- is based on the package Thermal-FIST. It is used here to study the effect of excluded volume on cumulants of the (net-)proton number distribution in central collisions of heavy ions in a broad collision energy range in conjunction with exact global conservation of baryon number, electric charge, and strangeness. The results are compared with earlier calculations based on analytical approximations, quantifying the accuracy of the latter at different collision energies. An additional advantage of the new method over the analytic approaches is that it offers the flexibility provided by event generators, making it straightforwardly extendable to other observables.